1. Field of the Invention
The present invention relates to a light emitting diode device, and relates more particularly to a light emitting diode device of high light-mixing efficiency that can have larger selection range of bins of light emitting diodes.
2. Description of the Related Art
Due to variations in manufacturing processes, characteristics such as intensities or wavelengths of fabricated light emitting diodes vary from one to another. When light emitting diodes were first introduced as lighting sources, most lighting sources utilized a single light emitting diode. In such arrangements, the influence of the variations between light emitting diodes is not significant.
However, when a plurality of light emitting diodes are arrayed for an application and are not first sorted, noticeable variations in color or luminous intensity may appear. To solve such issue, light emitting diodes are usually characterized in accordance with some parameters thereof. A bin code of each light emitting diode is determined based on test results. When an array of light emitting diodes is prepared for use, light emitting diodes having similar bin codes are selected so that arrayed light emitting diodes will not have non-uniformity issues. Nevertheless, the sorting of light emitting diodes increases cost, and in addition, with the utilization of devices for large luminous area and the requirement of luminous quality, the numerical range of bin codes selected for an array of light emitting diodes is relatively narrowed, and the narrowing of the numerical range of bin codes causes inconvenience and cost increase.
Furthermore, the efficiency of phosphor powder declines with increasing in environmental temperature. Light emitting diodes are luminous devices with high heat generation, and if the design of the heat dissipation module is improper or the control of environmental conditions is poor, the efficiency of the phosphor powder will be affected. Thus, to maintain efficiency of the phosphor powder, further protection of the phosphor powder is required.
Compared to conventional backlight modules, backlight modules using light emitting diodes have a larger projection angle of light in one direction to mix light and at the same time, have a smaller projection angle of light in another direction to direct more light into the backlight module and increase luminous intensity. In summary, use of sorted light emitting diodes to make arrayed light emitting diodes can ensure the luminous quality; however, high cost will affect economic benefit. The efficiency of phosphor powder is influenced by temperature, but no solution is found in the conventional design. Moreover, when light emitting diodes are used in a backlight module, the light projection angles varying in different directions is required, but in the prior art techniques, no technology has been developed to address this issue.